In a recent article I discussed how to quickly and easily set up your iTunes library with your AppleTV. I also mentioned how much I have come to depend on and love my AppleTV. While the AppleTV is great, it can drive you crazy when things go wrong. For example, my AppleTV recently only played audio content from videos I was trying to play. Instead of rushing out to the Apple Store for warranty service, here are a few easy steps you can try.
1. Disconnect the AppleTV from the power source. Basically, unplug it. Leave it unplugged for a minute or two and plug it back in. This temporarily solved the audio/video issue I mentioned above.
2. Disconnect all video/audio cables from the AppleTV and the TV and reconnect them. It is possible you have a bad connection. You could even try using new cables to determine if you have a faulty cable.
3. Disconnect from iTunes and reload your content. You can do this in the settings menu for iTunes libraries. Once you sever the connection to your iTunes library the AppleTV will lose all of its content. You have to reconnect (by syncing the library with the AppleTV and using the code the AppleTV provides - check the article linked to above) and reload all of your content. It is almost like starting from scratch without reformatting the AppleTV.
4. As a last resort, you can reformat the AppleTV to factory settings. This will erase the AppleTV and restore the system software that it came with. Essentially, it is making it like it was when you bought it. Any software updates you downloaded will have to be redownloaded and installed. Of course, you will have to relink to iTunes and reload your content.
As I said this is the last resort. This was the only way I was able to fix my AppleTV issue. Once I reformatted and reloaded the content it has been working great. Of course, now that I say that I'll go home and it will have the same problem or a new one!
If any of the above steps fail to work it is time to take a trip to the Apple Store or call Applecare for service. There isn't too much more that you can do on your own.
Good Luck!